1. Field of the Invention
This invention relates to microstrip transmission lines and microstrip transmission line components operating in the millimeter wave region of the frequency spectrum and more particularly to a microstrip modulator/switch for use with such microstrip transmission lines and microstrip components.
2. Description of the Prior Art
Modulator/switch devices suitable for use with microstrip transmission lines and microstrip components operating in the millimeter wave region of the frequency spectrum have not heretofore been developed. Since much equipment has been developed today for use in the millimeter wave region of the frequency spectrum and since such equipment is often designed with planar circuitry utilizing microstrip transmission lines and microstrip components because of the substantial savings in size and weight achieved thereby, a need has arisen for a microstrip modulator/switch which is capable of operating in this region of the frequency spectrum. For example, such microstrip modulator/switch devices could be used to modulate millimeter wave energy for various systems applications or could be used as a protective type switch in radar systems and the like to protect sensitive millimeter wave receivers during the time that the millimeter wave transmitter is transmitting.
Essentially, a nodulator/switch device suitable for use in the millimeter wave frequency region must provide a useful change in insertion loss for the device when the device is actuated. The device should have a first transmission state in which it provides a low attenuation of the applied RF electromagnetic wave signal and consequently exhibits a low device insertion loss and a second transmission state in which it provides a high attenuation of the applied RF signal and exhibits a high device insertion loss. The device must also be capable of being switched from one of the foregoing states to the other with only a minimum amount of switching energy. For example, when the device is used as the aforementioned protective switch for radar applications and the like, the device would be placed in the high loss state during the time that the radar transmitter is transmitting to protect the receiver of the radar set from the transmitted pulse and then actuated to the low loss state when the transmitter is not operating.
A suitable microstrip modulator/switch for use in the millimeter wave frequency region should also have a mechanically-rugged construction which is light in weight, compact in size and which is relatively inexpensive to manufacture and maintain. Because devices exhibiting the aforementioned useful change in insertion loss or attenuation characteristics are often called upon to act not only as switches but also as modulators, the term "microstrip switch" as used hereinafter in the specification and claims of this application shall be deemed to mean a device which is capable of functioning both as a modulator and a switch.